Fasteners are known for joining conveyor belts, belts and similar products which comprise hinge elements and are likely to be fixed astride an end of a conveyor belt, the hinge elements being able to be placed between similar hinge elements, belonging to a similar fastener fixed at the other end of the conveyor belt, the two fasteners being linked by a linkage and articulation pin passing alternately through a hinge element of one of the fasteners and then through a hinge element of the other of the fasteners.
This general type of fastener can be linked to the end of a conveyor belt by rivets, nut and screw systems, flange-back nails, twin-point staples. These rivets, screws, nails or staples are passed through holes already pierced in the upper half of the fastener, crossing through the conveyor belt, and then through holes already pierced in the lower half of the fastener, and are locked from the other side by forming a second rivet head, by tightening a screw, or by bending the ends of the nails or the twin point staples.
The major problem faced by these very rigid fixation systems is the rupture of the rivets, screws or pins of nails or staples, caused by the strains undergone by these rigid assemblies when the conveyor belt is operated under severe conditions. Even the twin point staples can break, in particular because of the strains imposed when the conveyor belt passes over the forward or backward rollers. Such breaks cause damage and involve repeated stoppages for repairs.
The aim of the present invention is to develop a new fastener for conveyor belts in which the means of fixation is constituted of screws, but in which the ensemble of the means used allows a certain flexibility of screw linkage of the two halves, upper and lower, of the fastener, this flexibility being indispensable to ensure the lifetime of the linkage and/or fastener, because of the difference between the path of the lower face and the upper face of the conveyor belt, at the moment of passage over the forward and backward rollers.
This problem is solved by using a joining fastener for the conveyor belt, comprising two fixation plates linked by U-shaped hinge elements presenting, in one of the fixation plates, holes allowing the passage of a screw and holding its head and in the other fixation plate dimplings which are oriented towards the first fixation plate, the screws passed through the holes of the first fixation plate being able to be screwed in the dimplings which are arranged in line with the corresponding holes of the first fixation plate when the fastener is tightened on a conveyor belt end, characterised in that the dimplings, at their base, present steps extending over a part of their external circumference, but separated by two circular sectors without diametrically opposed steps, generally oriented in the longitudinal direction of the conveyor belt on which the fastener according to the invention is set (or will be set), the material of the fixation plate being sheared at the position of these non-deformed circular sectors so as to allow the formation of the step partially surrounding the dimpling by stamping of the base plate.
In an embodiment of the invention, the dimpling is threaded internally for the pitch of the screws used to fix the fastener on the end of the conveyor belt. However, such threading is not absolutely necessary since when the dimpling has a smooth surface, the use of self-threading screws gives an excellent grip, especially since in the case of normal use, these screws are never unscrewed and re-screwed.
Advantageously the holes in one of the fixation plates destined for the passage of screws are given an opening in the form of a cup allowing the screw heads to lodge there so that they do not pass through the external face of the fastener.
As the steps made by stamping the dimplings form a cup on the external side of the plate provided with dimplings, even if the screws pass a little further than the chimney of the dimpling, the length of the screws can be such that the end of the screws does not go beyond the plane of the external face of the fixation plate provided with dimplings, that is to say that the end of the screws is in the space comprised between the base of the dimpling chimney and the plane of the external face of the fixation plate provided with dimplings.
Thus, the joints do not have any asperities which, otherwise, could be constituted of screw heads or their ends.